The present invention relates to the field of quantitative microspectroscopy, and in particular to a method for determining the volume of particles that are suspended in liquids.
In many areas of science, medicine and technology, there exists a need to determine the volume of small particles in liquids. Often, the volume of individual particles is of interest, but in other cases the relative volume content of a whole population of particles within a liquid volume has to be determined. A typical example is related to the determination of the mean volume of the red cells in blood, and to the determination of the relative volume content of the red cells in a given blood volume, which is called hematocrit.
Usually, the hematocrit is determined by centrifugating a given volume of blood, measuring the column height of the red blood cells, measuring the overall height of the centrifugated sample, and calculating the ratio of the two. The volume of single cells is most often determined by using flow cytometers or impedance counters.
All of these methods require pre-processing steps that make the test relatively labor-intensive and costly. Moreover, the instrumentation involved can be extremely expensive. Consequently, there exists a need for a simple and inexpensive method for determining the volume of single particles and for the determination of the relative volume content of a whole particle population within a given volume of liquid.
It is an objective of the present invention to provide a method for determining the volume of particles that are suspended in liquids.
According to the present invention, the above objective is achieved by depositing a liquid sample that contains suspended particles into an optical cuvette having an entrance window and an output window at a known distance from each other, by adding and evenly distributing a light-absorbing dye into the liquid sample that does not leak into the suspended particles, by sending light of such a wavelength through the cuvette that is highly absorbed by the added dye, but only weakly absorbed by the suspended particles, by measuring the optical transmission through the cuvette in an area that contains no particles, by measuring the optical transmission through the cuvette in an area that contains particles, and by calculating the volume of the suspended particles based on these transmission values and the known distance of the cuvette windows.